It sounds like you (and others) just like to make excuses for Nylander.
I'm a Nylander fanboy. That's why I try to distance myself from bias and look at things as analytically as possible.
Nylander has terrific shot metrics across the board, including those that take quality into account. He has set up more passing opportunities than most of the league, even when taking quality into account. Over the last few years, he's in the same group as Marner and Matthews in terms of individual chance generation. This season he and Kapanen are slightly behind those two and Tavares. Like I said last week, I got a look at some tracking data and Nylander had the second most slot passes on the team, was our best transition player, second best in individual puck possession, was in the top group in forced turnovers from forecheck. Last year he led the league in neutral zone stick checks, and led the team in neutral zone defensive plays. I don't have this years data. I've tracked his game as a center so far since I've been interested in his defensive game, and he has the most zone exits with possession on the team while also leading the team in slot passes blocked, as well as takeaways in the defensive zone*.
At some point you have to look elsewhere, because absolutely
everything points towards him being a great player that we don't get enough out of. How to do that? Perhaps play him on a proper scoring line, where he has been a top 30 forward. Perhaps put him on our only effective PP unit, since he's been a top 10 player in primary point production when he's been on one. Perhaps don't put him on a line with some of our worst forwards offensively, including the guy where the duo has the worst chemistry in the entire league.
Talking about excuses is a cop out. There's nothing to gain by ignoring the above, other than a less informed, less accurate picture.
P.S I really don't think that looking at pre and post-return numbers on a team level is a good way to see his impact. Matthews produced worse after Nylanders return, yes. He has done that with or without Nylander, and it pre-dated Nylander coming back as well. I'm not sure how you can look at my data that looks at what has happened with Nylander on the ice and call it an excuse, and then turn around with your own contextual analysis and partially draw conclusions on things that happen when he's on the bench.
* Those last two has been pretty much the same thing, as he's basically intercepted the puck and moved it up, rather than just block it.